This invention relates to a chimney coupling provided between a chimney inlet duct and the outlet end of a flue gas pipe. The coupling has a compensator (heat expansion equalizer), one end of which is attached to the flue gas pipe and its other end, oriented towards the chimney, has a radially projecting flange which, by means of clamping devices engaging its reverse face, is pressed into sealing engagement with chimney portions surrounding the inlet opening of the duct.
A known chimney coupling of the above type comprises a frame formed of welded metal bars of L-shaped cross section. The frame has a tubular portion which projects into the lateral inlet opening of the chimney duct and which maintains a radial clearance therewith. The frame further has an essentially planar flange which, with the interposition of a ceramic fiber insert, is pressed, by means of screws, against the chimney portion surrounding the duct inlet. The intermediate space between the tubular part and the chimney inlet is filled with mortised asbestos cords and closed off by a sealing mass. The tubular portion of the frame continues outwardly and terminates in a radially outwardly projecting flange portion on which there is held, by means of a clamping bar, a radially outwardly projecting flange of a compensator, whose other end is secured to the flue gas pipe in the same manner. Because of the strong corrosive effect of the flue gases and the entrained or precipitated condensate, it has been necessary to make the above-noted frame of high-grade steel, involving significant expense. Further, large pressing forces have been needed to ensure that the ceramic fiber material has a certain sealing effect. Such forces, however, have led to an excessive load on the chimney masonry. Due to the different heat expansion of the frame relative to the chimney inlet during shutoff or startup, risks of loosening of the components and thus a deterioration of the seal have appeared.